Washing a roof was generally considered a low-pressure contact sport in the “old days”. Before the creation of contemporary tools and techniques, you had to climb onto the roof with a pressure washer wand or a surface cleaner to get the job done. This involved significant risk of falls. If you use this method, be sure to use all appropriate safety gear when climbing on any roof. Never attempt cleaning a roof without taking all proper safety precautions; even the flattest roof can become slippery and hazardous when wet.
To clean a roof this difficult and dangerous old-fashioned way, you would drag the pressure washer hose or surface cleaner up on to the roof using a ladder. Moving around to reach areas was dangerous, since the slanted surface was soon covered with soapy cleaner.
Avoid walking on buckled shingles and avoid obviously sagging areas. On many older roofs you will be able to see where the roof joists are located, and putting your weight on these spots is likely to cause no damage whatsoever.
Look for cracks around roof projections (chimneys, vents, etc) and avoid getting water near these problem areas.
To walk on a roof, you should have safety rigging that meets OSHA guidelines. This will likely involve a body harness tied off to a structure on the opposite side of the home and shoes designed for walking roofs. This sort of equipment can be found at Safety stores. Many contractors still walk roofs to clean, but safety equipment is available now that was not available years ago that make the job easier and safer.
One company now makes a roof anchor that simply slips down into roof vent pipes, for example. This allows you to move around reasonably freely, secure from the danger of a fall to the ground. It is a lot smarter than tying off to the bumper of a vehicle (the source of many urban legends in this business).
If walking the roof does not excite you, there are at least two alternatives. One is to use a man-lift such as the one pictured here. You can spray the roof from this secure perch without danger of slipping.
Another alternative is to work from the ground or from the roof edge. It takes specialized equipment to make this technique effective, but this is the safest imaginable way to get the job done. We will explain all this in our upcoming posts. Commercial restorations roof cleaning process involves techniques which are safe and guarantee best results after cleaning is done.